Poly(arylene ether)-polyolefin compositions are well known. Many references teach the desirability of preparing these compositions by combining all components in a single mixing step. See, for example, U.S. Pat. No. 4,764,559 to Yamauchi et al.; U.S. Pat. No. 4,772,657 to Akiyama et al.; U.S. Pat. No. 4,863,997 to Shibuya et al.; U.S. Pat. No. 4,985,495 to Nishio et al.; U.S. Pat. No. 4,990,558 to DeNicola, Jr. et al.; U.S. Pat. Nos. 5,071,912, 5,075,376, 5,132,363, 5,159,004, 5,182,151, and 5,206,281 to Furuta et al.; U.S. Pat. No. 5,418,287 to Tanaka et al., and European Patent Application No. 412,787 A2 to Furuta et al.
Alternatively, some references teach the desirability of adding components in order of higher to lower viscosities. See, for example, U.S. Pat. No. 4,764,559 to Yamauchi et al., U.S. Pat. No. 4,985,495 to Nishio et al., and U.S. Pat. No. 5,418,287 to Tanaka et al.
In yet another proposed blending method, a polyphenylene ether and a polypropylene-graft-polystyrene copolymer, with or without unmodified polypropylene, are pre-mixed before one or more rubbery substances are added with additional mixing. See, for example, U.S. Pat. Nos. 5,071,912, 5,075,376, 5,132,363, 5,159,004, 5,182,151, and 5,206,281 to Furuta et al.; European Patent Application No. 412,787 A2 to Furuta et al.; and Japanese Unexamined Patent Application 63[1988]-113049 to Shibuya et al.
The above-described methods produce compositions that are inadequate for many commercial uses because they exhibit excessive variability in key properties, including stiffness and impact strength. There remains a need for a method of producing poly(arylene ether)-polyolefin compositions having improved property balances. In particular, there remains a need for a method of producing poly(arylene ether)-polyolefin compositions exhibiting reduced property variability and improved tradeoffs between stiffness, impact strength, and heat resistance.
The above described and other drawbacks and disadvantages of the prior art are alleviated by a method of preparing a thermoplastic composition, comprising: melt-blending to form a first intimate blend comprising a poly(arylene ether), a poly(alkenyl aromatic) resin, a hydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene; and an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene; and melt-blending to form a second intimate blend comprising the first intimate blend, and a polyolefin.